1. Field of the Invention
The invention relates to a semiconductor wafer planarizing device and a method for planarizing a surface of a semiconductor wafer by polishing it, more particularly, to the semiconductor wafer planarizing device having a polishing pad made of different kinds of material on its surface.
2. Cross-Reference to Related Application
This application claims the priority benefit of Japanese Patent Application No. 10-160685, filed Jun. 9, 1998, the entire subject matter of which is incorporated herein of reference.
3. Description of the Related Art
Generally, a semiconductor device has a multi-layered structure which is comprised of conductive layers and insulating layers. The surface of an insulating layer formed on a patterned conductive layer is uneven generally because of a pattern of the conductive layer. As another conductive layer which is formed on the uneven insulating layer surface may not be patterned in an expected manner, the surface of the insulating layer should be planarized.
A device that has been used to planarize a semiconductor includes a polishing pad supported by a turntable which is rotated by a turntable motor. When the semiconductor wafer is held by a wafer chuck, the wafer is pressed by the wafer chuck against the polishing pad. The wafer chuck is rotated by a wafer chuck motor to polish the surface of the semiconductor wafer uniformly. As the wafer chuck is connected to an arm motor by a wafer chuck supporting arm and the wafer chuck motor, the wafer chuck is moved over the polishing pad by the arm motor. Slurry, which is a liquid for polishing having corpuscles, is applied to the polishing pad from a slurry supply nozzle. A method for planarizing the surface of the semiconductor wafer with such a semiconductor wafer planarizing device is explained below.
The turntable on which the polishing pad is placed is rotated, and pure water is then supplied onto the rotating polishing pad. The semiconductor wafer, which has an uneven surface, may be pneumatically held on the wafer chuck. Alternatively the semiconductor wafer may be held on the wafer chuck by surface tension of water. In any case, the wafer surface being polished is held so as to face the polishing pad. When the wafer chuck is rotated, slurry is ejected, in place of the pure water, from the slurry supply nozzle to the polishing pad, which continues to be rotated with the turntable. Then, the surface of the semiconductor wafer to be polished is pressed by the wafer chuck against the polishing pad. As the uneven surface of the semiconductor wafer is polished by friction between the semiconductor wafer and the slurry on the polishing pad, the surface of the semiconductor wafer is planarized.
Two kinds of polishing pad have been used. One is a hard type; the other a soft type. When the hard type of polishing pad is used, the shape of the polishing pad is of transformed by the pressure of the semiconductor wafer. Therefore, the surface of the semiconductor wafer is planarized. However, if the turntable is warped, the thickness of the polished layer will not be uniform, because the surface of the turntable and the surface of the semiconductor wafer will not be parallel. When the soft type of the polishing pad is used, the shape of the polishing pad is easily transformed by the pressure from the semiconductor wafer. Therefore, although the polishing is uniform, the surface of the semiconductor wafer is not planarized.